• Journal of Korea Water Resources Association
• /
• v.51 no.6
• /
• pp.515-521
• /
• 2018

Seawater intrusion areas were calculated in Yeosu region considering sea level rise and the effects of countermeasures for seawater intrusion were analyzed using SEAWAT program. The estimated seawater intrusion area was $14.90km^2$ in 2015. When we applied climate change scenarios the area was changed to $19.19km^2$ for RCP 4.5 and $20.43km^2$ for RCP 8.5 respectively. The mitigation effects by artificial recharge with total $50m^3/d$, $100m^3/d$, and $300m^3/d$ are from 3.75% to 10.68% for RCP 4.5, and from 5.82% to 10.77% for RCP 8.5 respectively. If we install barrier wall with the thickness 0.8 m, 1.3 m, and 1.8 m, the mitigation effects are from 6.67% to 12.04% for RCP 4.5, and from 6.17% to 14.98% for RCP 8.5 respectively. The results of this study can be used to be a logical means of quantitative grounds for policy decisions to prevent groundwater contamination by seawater intrusion and subsequent secondary damage in coastal areas.

• Journal of KIISE:Computing Practices and Letters
• /
• v.13 no.4
• /
• pp.231-239
• /
• 2007

This paper presents the trade-off relationship between area and performance in the hardware design space exploration for the Korean national standard 128-bit block cipher algorithm SEED. In this paper, we compare the following four hardware design types of SEED algorithm : (1) Design 1 that is 16 round fully pipelining approach, (2) Design 2 that is a one round looping approach, (3) Design 3 that is a G function sharing and looping approach, and (4) Design 4 that is one round with internal 3 stage pipelining approach. The Design 1, Design 2, and Design 3 are the existing design approaches while the Design 4 is the newly proposed design in this paper. Our new design employs the pipeline between three G-functions and adders consisting of a F function, which results in the less area requirement than Design 2 and achieves the higher performance than Design 2 and Design 3 due to pipelining and module sharing techniques. We design and implement all the comparing four approaches with real hardware targeting FPGA for the purpose of exact performance and area analysis. The experimental results show that Design 4 has the highest performance except Design 1 which pursues very aggressive parallelism at the expanse of area. Our proposed design (Design 4) shows the best throughput/area ratio among all the alternatives by 2.8 times. Therefore, our new design for SEED is the most efficient design comparing with the existing designs.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2019.05a
• /
• pp.258-258
• /
• 2019

계산 격자에 기반하여 천수 흐름을 모의할 때, 그 격자에 담긴 물의 양을 정확하게 파악할 필요가 있다. 예를 들어, 초기조건으로 수위가 부여된다면 계산격자의 기하 특성에 맞추어 흐름 변수인 수심이나 흐름 단면적으로 바꾸어야하기 때문이다. 필요에 따라서는 모의 결과를 수위로 보이거나 격자 속 수심을 계산에 사용할 수도 있으므로 그 역변환도 고려되어야 한다. 2차원의 삼각형 계산격자에 대해서는 물의 부피와 수위 관계(volume/free-surface relationship)가 이미 정확(exact)하게 구명되어 있다(Hwang, 2017, J. KWRA). 그런데 1차원 문제의 횡단면에서 흐름 단면적과 수위의 관계(area/free-surface relationship)는 수위로부터 면적 환산에 대해서는 정확하나 그 역변환은 그렇지 않다. 매 시간 단계에서 갱신된 흐름 단면적으로부터 수위를 환산하기 위해 미리 작성된 면적-수위 자료를 이용한 선형 보간이 적용된다(Goodell, 2011, The RAS Solution). 이때, 환산 정확도는 자료의 해상도에 의존된다. 다행히 하천 횡단면 대부분을 채워 흐르는 홍수모의에서는 이 문제가 그리 심각하지는 않다. 심지어 수위가 복단면 저수로 턱에 걸쳐있어 흐름단면적이 급변하는 경우에도 환산 수위의 정확도는 크게 훼손되지 않는다. 그러나 미미한 환산 오차일지라도 그로 인해 수위가 저수로 턱을 넘거나 그보다 작을 수 있다. 이 경우, 홍수터의 잠김여부에 따라 수면폭(top width)이 실제 계산 결과에 비해 크게 달라질 수밖에 없다. 수면폭 오차는 그것을 이용하여 결정되는 수리 수심(hydraulic depth)이나 평균 하상고(mean bed level)의 산정에도 전파된다. 이 연구에서는 하천 횡단면에서 수위와 흐름 단면적 사이의 환산 정확도를 크게 높일 수 있는 기법을 제시하였다. 먼저 하천 횡단면에서 주어진 수위에 대해 흐름 단면적을 산정할 수 있는 알고리듬을 보였다. 또한, 횡단면에서 수위와 흐름 단면적의 관계가 단조 증가 함수(monotonically increasing function)임에 착안하여 그 역변환에 대해 해 찾기(root finding) 방법의 하나인 Brent 기법을 적용하였다. 이 기법은 주어진 구간에서 도함수가 알려져 있지 않은 경우에 대해서도 효과적으로 해를 찾을 수 있는 것으로 알려져 있다(Press et al., 2002, Numerical Recipes in C, 2nd Ed.). 내성천 하류 수계의 333개 단면에서 수면폭에 대한 상대 오차를 살펴보면, 선형 보간에 의한 기존 방법으로는 면적-수위 자료의 수가 1,000개가 되어도 그 최대치가 1% 이내에 들지 않은 반면, 이 연구에서 제시한 기법으로 면적-수위 자료 없이도 1% 이내로 줄어드는 것을 확인하였다. 다만, 반복 계산에 의한 계산 시간의 증대를 피할 수 없다. 미리 작성된 면적-수위 자료를 이용하면 계산 비용을 줄일 수 있으며, 약 35개의 구간으로 나누었을 때 비용 대비오차가 적절하였다. 이 연구는 한국건설기술연구원(주요사업 과제번호: 20190116-001)의 지원에 의한 것이다.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.25 no.4
• /
• pp.376-386
• /
• 2023

Due to climate changes, landslide hazards in the Republic of Korea (hereafter South Korea) continuously increase. To establish the effective landslide mitigation strategies, such as erosion control works, landslide hazard estimation in the long-term perspective should be proceeded considering the influence of climate changes. In this study, we examined the change in landslide-damaged areas in South Korea responding to climate change scenarios using the multivariate regression method. Data on landslide-damaged areas and rainfall from 1981-2010 were used as a training dataset. Sev en indices were deriv ed from rainfall data as the model's input data, corresponding to rainfall indices provided from two SSP scenarios for South Korea: SSP1-2.6 and SSP5-8.5. Prior to the multivariate regression analysis, we conducted the VIF test and the dimension analysis of regression model using PCA. Based on the result of PCA, we developed a regression model for landslide damaged area estimation with two principal components, which cov ered about 93% of total v ariance. With climate change scenarios, we simulated landslide-damaged areas in 2030-2100 using the regression model. As a result, the landslide-damaged area will be enlarged more than the double of current annual mean landslide damaged area of 1981-2010; It infers that landslide mitigation strategies should be reinforced considering the future climate condition.

• Journal of Practical Agriculture & Fisheries Research
• /
• v.4 no.1
• /
• pp.70-79
• /
• 2002

This study was conducted to determine correlations and combining abilities of leaf lengths, leaf widths, petiole lengths, number of branches, number of leaves, leaf areas, fresh weights, dry weights and number of flowers in F₁ crosses made with the partial seven-parent diallel cross in Viola tricolor. Leaf lengths and leaf widths showed highly positive correlation with petiole length and negative correlation with number of branches, number of leaves and number of flowers. There was positive correlation between the number of leaves and flowers as well as between leaf area and fresh weight. Mean squares of general combining ability(GCA) and specific combining ability(SCA) were highly significant for all the parameters. Variance component values of SCA were greater than those of GCA for all the parameters except leaf length, implying preponderance of non-additive gene actions for these characters. The lines C and G for leaf lengths and widths, the lines A and F for number of leaves, the lines A, B and G for leaf areas, and the lines B and F for number of flowers showed relatively high GCA effects. The crosses of A×B and B×D exhibited high SCA effects on increasing leaf lengths, leaf widths, number of leaves, fresh weights and number of flowers. And also the crosses of B×E and D×G exhibited high SCA effects on decreasing leaf lengths, leaf areas and fresh weights as well as increasing number of flowers. The broad sense heritabilities of most characters were high compared with the narrow sense one. Those of leaf length, leaf width, petiole length and number of leaves were high in both the broad and narrow sense heritabilities.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.16 no.6
• /
• pp.553-560
• /
• 2014

The road tunnel install a vent for the purpose of ventilation and smoke control. Ventilation equipment capacity(number of jet fans) depends on from the condition that of the pressure and ventilation resistance. Pressure and the resistance under operating vehicle have affected on the drag coefficient. The drag coefficient of the tunnel have affected by the blockage effect and slipstream effects. However, when calculating the ventilation fan, are not properly consider taking into account such effects. Therefore, ventilation force may have been slightly overestimated. This paper describes the drag coefficient through a numerical analysis to calculate the equivalent resistance area that reflects the vehicle distance, and examined the equivalent resistance area. The ventilation coefficient corresponding to the result heavy vehicle mixing ratio of the present study was not clear. Equivalent resistance area had reduced by about 86% compared to the road design handbook current standards. Also it had analyzed and reduced to 62.2% compared to Korea Highway Corporation ventilation design criteria ratio, which is the old standard.

• Journal of Korean Society on Water Environment
• /
• v.31 no.1
• /
• pp.12-18
• /
• 2015

In this research, the hydrologic effects between a pre-existing urban landuse and low impact development (LID) applied conditions were compared and evaluated. The infiltration trench and tree box filter that were utilized in LID represent only 1% of the catchment area that they drain. Storm event monitoring were conducted from July 2010 to July 2014 on a total of 22 storm events in both LID sites. After LID, hydrological improvement was observed as the sites exhibited a delay (lag time) or reduction in the magnitude, frequency and duration of runoff and flow peaks as the rainfall progress. In addition, the maximum irreducible peak flow reduction for infiltration trench was found to be 61% and 33% for the tree box filter when rainfall was 40 mm and 30 mm, respectively. In designing LID, it is recommended to consider the storage capacity and catchment area, as well as the amount of rainfall and runoff on the site.

• Journal of Korea Water Resources Association
• /
• v.39 no.2 s.163
• /
• pp.121-126
• /
• 2006

Snowmelt effect is identified from the analysis of the relationship between precipitation and groundwater level(GWL) data and Severe drawdown of GWL is observed in drought. Groundwater dam Operation Index (GOI), which is developed for the optimal operation of groundwater dam, is calculated by taking common logarithm of the moving average(MA) of precipitation data for a certain period. The period can vary from watershed to watershed because the period is decided by picking the maximum correlation coefficient between GWL and GOI of several MAs of precipitation. For Ssangchun watershed, the correlation was the strongest when we apply 70 day MA for GOI calculation. Snowmelt effect is considered by applying the temperature change by elevation($0.5^{\circ}C$ decrease per 100m) and examining the areal distribution of the watershed by elevation. Snow event is assumed when the daily average temperature is below $0^{\circ}C$ and snowmelt is assumed when the temperature is above zero degree Celsius. Total snowmelt is assumed for the day. When the snow event is occurred the precipitation data is separated into two components, snow and rainfall. The areal distribution by elevation is used for the calculation in the separation. The correlation between GWL and GOI is higher when we consider snowmelt effect than we neglected it.

• Korean Journal of Environmental Biology
• /
• v.38 no.4
• /
• pp.705-713
• /
• 2020

The present study investigated the temporal changes of river habitats caused by construction and operation of the three large weirs (Sejong, Gongju, and Baekje) in the Geum River. High resolution satellite imagery taken during three periods (preconstruction, before and after gate operation) were used for habitat analysis. We divided bar area into eight habitat types in addition to water area. Then, we identified the nine habitat types from the satellite imagery and estimated each habitat area. Our results show that after weir construction, large bar areas were dramatically decreased and bareland was nearly absent post gate-operation in all three weirs. However, total bar area and bareland were again increased distinctively soon after weir opening events, especially in the uppermost weir, the Sejongbo. These results suggest that weir opening operations provide a relatively simple channel of more diverse through the process of increasing bar area in a river channel.

• Ecology and Resilient Infrastructure
• /
• v.8 no.1
• /
• pp.44-53
• /
• 2021

The flood prevention capacity of drainage facilities in urban areas has weakened because of the increase in impervious surface areas downtown owing to rapid urbanization as well as localized heavy rains caused by climate change. Detention can be installed in trunk sewers and linked to existing drainage facilities for the efficient drainage of runoff in various urban areas with increasing stormwater discharge and changing runoff patterns. In this study, the concept of detention in trunk sewers, which are storage facilities linked to existing sewer pipes, was applied. By selecting a virtual watershed with a different watershed shape, the relationship between the characteristic factors of detention in the trunk sewer and the design parameters was analyzed. The effect of reducing stormwater runoff according to the installation location and capacity of the reservoir was examined. The relationship between the installation location and the capacity of the detention trunk sewer in the Dowon district of the city of Yeosu, South Korea was verified. The effects of the existing water runoff reduction facility and the detention trunk sewer were also compared and analyzed. As a result of analyzing the effects of reducing internal inundation, it was found that the inundation area decreased by approximately 66.5% depending on the installation location of the detention trunk sewer. The detention trunk sewer proposed in this paper could effectively reduce internal inundation in urban areas.